LoadTimeWeaver which uses reflection to delegate to an underlying ClassLoader
with well-known transformation hooks. The underlying ClassLoader is expected to
support the following weaving methods (as defined in the LoadTimeWeaver
interface):

public void addTransformer(java.lang.instrument.ClassFileTransformer):
for registering the given ClassFileTransformer on this ClassLoader

public ClassLoader getThrowawayClassLoader():
for obtaining a throwaway class loader for this ClassLoader (optional;
ReflectiveLoadTimeWeaver will fall back to a SimpleThrowawayClassLoader if
that method isn't available)

Please note that the above methods must reside in a class that is
publicly accessible, although the class itself does not have to be visible
to the application's class loader.

The reflective nature of this LoadTimeWeaver is particularly useful when the
underlying ClassLoader implementation is loaded in a different class loader itself
(such as the application server's class loader which is not visible to the
web application). There is no direct API dependency between this LoadTimeWeaver
adapter and the underlying ClassLoader, just a 'loose' method contract.

This is the LoadTimeWeaver to use in combination with Spring's
TomcatInstrumentableClassLoader
for Tomcat 5.0+ as well as with the Resin application server version 3.1+.